I have a 2003 civic ex that in the past 6 months is a complete dog/no power with a cylinder 4 misfire. I have changed the spark plugs, #4 coil, and #4 fuel injector. None of these have fixed the sluggishness or code. I have not done a compression check and it has not had the timing belt done yet. I am getting frustrated with the problem. I would appreciate any suggestions. Thanks!

 

only other things that you haven't changed that could cause single cylinder misfire are vacuum leak or compression related issue (possibly tight/burned valves?) or a bad ECM /wiring between ECM and coil(causing coil to not fire).
last but not least blown headgasket....

i say start with compression test to know engine baseline is good , then smoke test for vacuum leak, then advanced testing with scope will be required to test ECM/wiring/coil output